Restrictive manipulation limited try mechanism for a combination lock

ABSTRACT

A combination lock having a restrictive manipulation or limitedtry feature to prevent the opening of the lock by trial and error manipulation. The mechanism recognizes and counts each unsuccessful attempt at finding the proper code. After a predetermined number of unsuccessful attempts to open the lock, the mechanism renders the lock unopenable, without the knowledge of the illicit manipulator but will continue to accept additional manipulations. A registering device, associated with the mechanism, will reset to permit the opening of the lock by the owner only when the proper code is dialed before the predetermined number of unsuccessful attempts has been reached.

United States Patent [1 1 Swaim Jan. 22, 1974 [22] Filed:

[ RESTRICTIVE MANIPULATION LIMITED TRY MECHANISM FOR A COMBINATION LOCK[75] Inventor: Frank H. Swaim, Silver Spring, Md.

[73] Assignee: The United States of America as represented by theSecretary of the Navy, Washington, DC.

June 23, 1972 211 Appl. No.: 265,930

[52] US. Cl. 70/333 R, 70/DIG. 49 [51] Int. Cl E05b 37/08 [58] Field ofSearch 70/15, 1.7, 333 R [56] References Cited UNITED STATES PATENTS1,626,106 4/1927 Tibbetts 70/304 2,442,688 6/1948 Hendlin 2,587,6543/1952 Sammons 70/].7

Primary ExaminerAlbert G. Craig, Jr. Attorney, Agent, or FirmR. S.Sciascia; J. A. Cooke; Donn McGiehan [5 7] ABSTRACT A combination lockhaving a restrictive manipulation or limited-try feature to prevent theopening of the lock by trial and error manipulation. The mechanismrecognizes and counts each unsuccessful attempt at finding the propercode. After a predetermined number of unsuccessful attempts to open thelock, the mechanism renders the lock unopenable, without the knowledgeof the illicit manipulator but will continue to accept additionalmanipulations. A registering device, associated with the mechanism, willreset to permit the opening of the lock by the owner only when theproper code is dialed before the predetermined number of unsuccessfulattempts has been reached.

12 Claims, 3 Drawing Figures RESTRICTIVE MANIPULATION LIMITED TRYMECHANISM FOR A COMBINATION LOCK BACKGROUND OF THE INVENTION Thisinvention relates generallyto locks for securing a depository and, moreparticularly, to manipulationproof combination locks. Combination locksare thought to provide good security against unauthorized entry becausethey require a certain succession of numbers to be set on a dial to gainentrance. However, present combination locks are vulnerable tomanipulation by a knowledgable expert using the sense of feel, sight andsound and given enough time to make a number of trial combinations ofnumbers to finally open the lock. A background study of the owner of thelock, including his birthdate, his wife s birthdate, anniversary date,childrens birthdates, etc., will often provide the required combinationto the particular lock. However, even with this knowledge and skill, anexpert will have to make a number of manipulations or trials before hefinds the successful combination of numbers. If the combination lock wasprovided with a mechanism which would render the lock unopenable after apredetermined number of unsuccessful tries, the security of thedepository would be greatly enhanced.

Locks have a long history of providing good security againstunauthorized entry to dwelling houses, vehicles, safes, cabinets,.andother such security depositories. Key locks having a keyway and,therefore a hole, permit entry into the internal mechanism of the lockand allow manipulation of the tumblers with a pick and turning device;This procedure, called picking, will readily open any key lock.Combination locks are far superior to key locks because there is nokeyway or ready entrance into the internal mechanism for a key or addingnitroglycerin. Combination locks require a certain succession of numbersto be set on an outer dial through a left and right pattern of rotationsof said dial before it may be' opened. The most sophisticatedcombination lock has 100 possible settings for each directional turn ofthe dial, and some require as many as seven directional turns. The mostcommon'type combination lock has three directionalturns, thus providingone million possible combination settings. A five directional turn lockwill provide billion possible combination settings. With these number ofpossible combinations, the average person would consider it animpossibility to open such a lock, but to a knowledgable expert, theyrepresent only a challenge. The vast number of possible combinations isof little concern to the expert manipulator who knows the characteristicof the lock and uses this knowledge to find the proper code to gainentry. His technique is to make a quantity of tries designed to minimizethe amount of manipulations of the dial and the amount of time spentopening the depository.

Attempts in the-past to increase the security afforded by combinationlocks have generally been directed to elimination of the possibility ofattack by forceable means, such as drilling into the lock so that thecombination may be set mechanically, or by adding heat and explosiveshields to reduce the possibility of attack by torch cutting or blowingopen the closure to the depository. Few, if any, attempts have been madeto solve the problem of surrepticious entry by manipulation of thecombination lock, because the general public is of the opinion thatmodern sophisticated locks cannot be manipulated to opening. But, asdiscussed above, these locks are susceptible to being manipulated toopening by a knowledgable expert, a fact known to those practicing inthe security field.

SUMMARY OF THE INVENTION Accordingly, an object of the present inventionis to enhance the security provided by a combination lock.

Another object of the invention is to provide additional intelligence toa combination lock.

A further object of the invention is to provide a combination lockhaving the ability to distinguish betweeen authorized manipulation andunauthorized manipulation.

A still further object of the present invention is to provide acombination lock with the ability to register the quantity of attemptsat manipulation.

Still another object of the present invention is to provide acombination lock which is able to incapacitate the locking mechanism toprevent opening without the knowledge of the manipulator.

Still another object of the instant invention is to provide acombination lock with provisions to automatically reset the registeringmechanism when authorized manipulation takes place prior to reaching thepredetermined number of unsuccessful attempts at manipulation.

A still further object of the instant invention is to provide a means incombination locks to re-establish the limited-try feature for againaccepting authorized attempts at manipulation after the predeterminednumber of attempts has been reached.

Briefly, these and other objects of the present invention are attainedby the use of a restrictive manipulation or limited-try mechanism whichsubstantially prevents opening the combination lock by trial and errormanipulation. This feature recognizes and registers each unsuccessfulattempt at finding the proper code and, after a predetermined number oftries, precludes the conventional fence-lever from entering the gates inthe tumblers, thus rendering the lock unopenable. The register mechanismwill continue to accept additional manipulations without the knowledgeof the illicit manipulator that he is locked out. The register device,however, will reset to permit the fence-lever to enter the gates uponapplication of the proper code, if the predetermined number ofunsuccessful attempts has not been reached, and thus will permit theopening of the lock by the owner.

The means by which the mechanism registers the number of unsuccessfultries at opening the lock includes a pawl in contact with thefence-lever and a spring loaded ratchet wheel against which the pawloperates. If the proper code in not set in, and the manipulator attemptsto open the locking bar of the typical combination lock, the fence-levercan not drop into the gates of the tumblers, but rather comes to rest onthe outer edge of the tumbler wheels. The fence-lever then slightlyrotates on the wheels and also makes contact with the pawl, thus pushingth ratchet wheel and registering-one stroke. If desired, the ratchetwheel may be coupled to an indicator on the face of the lock to indicatethe number of advances or strokes that the ratchet wheel has taken.Further, if desired, a keyway and special key may be provided to releaseand resetthe ratchet wheel to the original position. Also, an additionalset of tumbler wheels engaged by the limited-try mechanism can be usedto re-set the mechanism for a fresh start by the owner.

The invention involves a technique to restrict or limit the number oftries and attempts to find a lost or unknown code of a combination lock,as by an unauthorized person seeking entry to the depository bymanipulation or surrepticious entry. This feature will recognize anddistinguish between attempts at unauthorized and authorizedmanipulation. The feature can be made to limit the number ofunauthorized tries or attempts in search of the proper code, and apredetermined number may be designed into the mechanism. Then, for thepurpose of this discussion, the predetermined number may be establishedas five. Therefore, the manipulator in search of the unknown code islimited to five attempts to open the lock. Upon reaching the fifthattempt, the restrictive manipulation mechanism will perform itsfunction, causing the lock to become unopenable. In this state, the lockmechanism retains the ability to receive additional attempted codes andeven the proper code, but will cease to recognize any. The lock will nowrefuse to open and is permanently locked. Further, other functions thatthe limited try feature performs at the end of the fifth attempt may beto explosively blow up the lock, sound an alarm or bell, or otherwiseindicate that unauthorized manipulation has been underway.

An additional important ability of this invention is to recognize theproper code set into the combination lock before reaching the improperfifth attempt. When the proper code has been set up on the combinationlock dial, the limited-try feature recognizes it and automaticallyreturns the registering ratchet wheel to its original position. Thisfeature is considered necessary because it takes into account thepossibility of human error of the owner when he manipulates the lockwith the knowledge of the proper code but makes a mistake in dialing thecorrect numbers. He will exercise extreme care not to reach the fifthattempt at opening the lock wnen he knows he will be then permanentlylocked out.

This invention also automatically advises the master or owner of thesecurity depository that attempts at manipulation have taken place. Thisinformation will warn him to take precautionary measures to eliminatefurther illicit attempts at opening this combination lock. Theinformation may be provided by a window or dial on the face of the lockso that the master can observe the unauthorized manipulation attempts bythe tell-tale register. A visual indicator will also notify the observerthat the full number of unsuccessful tries has been made and that othermeans will now have to be used to open the depository.

Under emergency conditions, the limited-try feature will permit theowner to intentionally perform a lockout condition, thereby precludinganyone to open the lock. After the emergency, the owner can reset thelock to its functioning condition.

BREIF DESCRIPTION OF THE DRAWINGS A more complete understanding of theinvention and many of the attendant advantages thereto will be readilyappreciated as the same becomes better understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawings wherein:

FIG. 1 is a isometric view partially cut away showing the limited-trymechanism in association with a standard combination lock;

FIG. 2 is a plan view of the rear ofa combination lock partially cutaway to show the detail of the limited-try mechanism; and

FIG. 3 is a side view of a combination lock partially cut away showingthe details of the limited-try mecha msm.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now the drawings,wherein like reference numerals designate corresponding parts in theseveral views, there is shown in FIG. 1 generally a combination lock 10.The conventional lock comprises a casing 12, and a base 14 which is theinternal rear surface of the face plate secured to a door (not shown)with suitable fastener means.

The casing 12 contains a plurality of tumblers 16 mounted for rotationwith a shaft and a dial (both not shown). Each of the tumblers 16 has asuitable notch or gatee 18, all of which must be in proper alignment inorder to eventually nestle a fence-lever 24. Note FIGS. 2 and 3. Asshown in FIG. 2, forward of the said tumblers 16 is a drive wheel cam 20having a radially indented cam slot 22 therein. Coacting with the drivewheel cam 20 is a fence-lever 24 having an integral, rearward extendingbar 26 to co-acting with the gates 18 in the tumblers 16, best shown inFIG. 1. This construction, just described in general, is conventionalwith most combination locks and further details are consideredunnecessary.

The fence-lever 24, as shown in FIG. 2, is shown in two positions, onesolid and the other as dot-dash phantom to show its cooperation with alimited-try mechanism 28 according to the invention.

The limited-try mechanism 28, according to the present invention,comprises a pusher lever 30, also shown in one solid and the otherdot-dash phantom, mounted for rotation about a pivot screw 32. Pusherlever 30 has a surface which is contacted by the fence-lever 24 when anattempt is made to open the lock, and will hereinafter be furtherexplained. At an eccentric pivot point 34 on push lever 30 is attachedfor articulation a feeder pawl 36. Feeder pawl 36 is spring-biased intoengagement with the teeth of a ratchet wheel 40 by a spring 38 having anarm hooked over the back of the feeder pawl 36 and helically wound aboutthe eccentric pivot point 34. The ratchet wheel 40 is spring-biased forclockwise rotation by a helically wound spring 42, shown in FIG. 3,under the ratchet wheel 40. The ratchet wheel 40 is mounted for rotationon an axis 44 extending above the top surface of the ratchet wheel.Further, on the top surface of the ratchet wheel is a circular camsurface 46 interrupted by a notch 47. A lockout bar 48 is pivotallyattached to the extended portion of the axle 44 by a cross pin 50 and isin contact with and normally in a raised position on the circular camsurface 46. The ratchet wheel 40 is held from freely rotating clockwiseby a holding pawl 52 having a tooth engaging portion 51 and a leverportion 53 about a screw 54. The holding pawl 52 is spring-biased intoengagement with the .ratchet teeth by a spring 56.

In operation, assuming the normal manipulating procedure to open acombination lock with 5 sets of numbers and therefore 5 tumblers, thedial is first turned to the left or counterclockwise a minimum of sixtimes. This action causes the lock spindle to pick up all five tumblers.The dial is then stopped at the first number setting of the code of thecombination, thus aligning one of the gates in the tumbler with thefence-lever. The dial is then turned to the right passing the nextnumber four times and stopping on it the fifth time to align the secondtumbler. The dial is then turned to the left passing the third number ofthe code three times and stopping the fourth, then turned to the righttwo times past'the fourth number and stopping the third time, thenturned left once past the fifth number and stopping the second time.This procedure aligns the gates 18 of the five tumblers 16 with thefence-lever 24. v

The dial finally is turned to the right to zero thus aligning the camslot 22 of the drive wheel 20 with the fence-lever 24. Then, dependingon the type of lock, the dial is held on zero and the locking barlocated in the center of the dial is rotated, or the dial is continuedto be turned to the right. Turning the locking bar disengages the camwheel 20 and permits the spring-loacled fence lever 24 to enter thealigned gates 18 of the tumblers 16. By turning the dial further to theright, the bolt of the lock is withdrawn and the depository is opened.This normal manipulation procedure of the lock does not engage thelimited-try mechanism except at the end of the final opening turn whenthe fencelever 24 strikes the lever portion 53 of holding pawl 52 topivot the tooth engaging portion 51 out of engagement with the ratchetwheel 40 permitting it to rotate counterclockwise to the original resetposition.

For unauthorized manipulation in search of the proper code to open the'lock, the following action takes place. The manipulator turns the dialin the same sequence as oulined above with a selected set of numbers,perhaps from a list as previously described. When the dial is finallyturned to zero and the locking bar located in the center of the dial isturned or the dial is continued passed zero, and presuming the impropercode was inserted, the bar 26 of fencelever 24 contacts at least one ofthe edges of the tumblers 16 rather than entering the gates 18. Whenthis attempt or try is made to open the lock as by rotating the dial tothe right beyond zero, the fence-lever 24 now makes contact with thepush lever 30 which pushes the feeder pawl 36 into one of the teeth androtates the ratchet wheel 40 one stroke or one tooth position. Theholding pawl 52 engages the tooth next advanced by the bias of spring 56and holds the ratchet wheel 40 in the counterclockwise advancedposition.

The unauthorized manipulator, after finding that the lock will not open,will no doubt insert a second combination of numbers and repeat theopening operation. Again, if the proper combination has not been set in,the bar 26 of fence-lever 24 will rest on the edge of the tumblers l6and when an attempt is made to open the lock, the fence rotates andmakes contact with the pusher lever 30 which subsequently advances theratchet wheel 40 another position counterclockwise. The limited-trymechanism has now registered the two attempts made to open the lock withthe wrong set of numbers. Without knowing this, the unauthorizedmanipulator continues inserting combination codes searching for theproper code that will open the lock.

Upon reaching the fifth attempt, the ratchet wheel 40 has been advancedto the fifth tooth position. In this position, the cam surface 46 on thetop surface of the ratchet wheel reaches a point where the lockout bar48 will fall into the notch 47 by virtue of the bias of spring 49 underthe crosspin 50. In this lockout position, any attempts, authorized orunauthorized, to open the lock, will cause the fence-lever to advanceand its inside surface 25 will strike the distal end of the lockout bar48 thereby precluding the bar 26 from entering the gates 18 of thetumblers 16. As can be now understood, the limited-try mechanism hasrendered the lock unopenable and the manipulator is completely lockedout. The locking mechanism will continue to refuse to recognize any codeof numbers set in, and the manipulator is unaware that this action hastaken place.

The master or owner of the depository will be aware of this conditionwhen he is sure that he has set in the proper code, because the lockrefuses to recognize the proper code. If desired in the construction ofthe lock, a hole may be provided to accept a special tool or key thatmay be inserted to release the holding pawl 52 from the ratchet wheel 40allowing the ratchet wheel to rotate clockwise by virtue of its springbias to its original position lifting the lockout bar 48 from behind thefence-lever 24.

This novel invention also recognizes that the owner of the depositorymay inadvertantly set in the improper code when attempting to open thecombination lock. From the prior discussion, it is obvious that he hasat least four tries. However, as is obvious from the prior discussion,the limited-try mechanism operates only when the combination has beenset in, the dial returned to zero, the locking bar in the center of thedial has been set, and an attempt is 'made to draw the bolt or open thelock. If, when the owner is dialing in the combination and realizes hehas inadvertantly set in an improper number, he should begin from thestart by redialing the proper combination. As soon as the propercombination of numbers has been used, prior to the lockout featureoperating at the fifth try, the limited-try mechanism will beautomatically reset.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that, within the scope of the appended claims, theinvention may be practised otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. An improvement in combination locks having tumblers with gates and afence-lever for improving the security thereof from unauthorizedmanipulation comprising a limited-try mechanism cooperating with saidtumblers and said fence-lever which prevents opening of the lock after apredetermined plurality of attempts have been made using the impropercombination, the action of said mechanism undetectable by amanipulation.

2. The improvement of claim 1 wherein said limited-try mechanismincludes blocking means preventing said fence-lever from cooperatingwith said tumbler gates to preclude the opening of the lock.

3. The improvement of claim 2 wherein said limited-try mechanism furtherincludes means for mechanically registering cumulatively the number ofunsuccessful attempts to open the lock.

4. The improvement of claim 3 wherein said limited-try mechanism furtherincludes reset means to permit opening the lock when the propercombination is used before the predetermined plurality of attempts havebeen made.

5. The improvement of claim 4 wherein said limitedtry mechanism furtherincludes means permitting resetting by a tool from the outside of thelock after the predetermined plurality of attempts have been made toopen the lock.

6. The improvement of claim 5 wherein said limitedtry mechanism furtherincludes means for monitoring the plurality of attempts to open thecombination lock on the face of the lock without notifying anunauthorized manipulator that the predetermined number has been reached.

7. The improvement of claim 2 wherein the limited-try mechanism furtherincludes means for actuating an alarm when the predetermined pluralityof attempts have been made to open the lock.

8. An improvement in a combination lock having tumblers with gates, acam wheel, a fence-lever, and a dial on the face comprising:

a limited-try mechanism comprising:

a pusher pawl cooperating with the fence-lever when it does not enterthe gates;

a ratchet wheel rotatably advanced one step by said pusher pawl eachtime the fence-lever comes in contact with said pusher pawl;

a holding pawl coating with said ratchet wheel to hold it in theadvanced position;

a cam surface having a slot on the side of said ratchet wheel;

a lockout bar in slidable relationship with said cam and coacting withand precluding the entry of the fence lever into the tumbler gates whensaid lockout bar enters said slot in said cam surface,

whereby said limited-try mechanism renders the lock unopenable after thepredetermined plurality of trys using the improper combination has beenmade and whereby said limited-try mechanism is reset by using the propercombination before the predetermined plurality of trys has been made.

9. The improvement of claim 8 wherein said limitedtry mechanism furthercomprises:

a tell-tale dial outside the lock and coupled with said ratchet wheel toindicate the plurality of attempts made to open the lock.

10. The improvement of claim 9 further comprising:

an alarm coupled with said limited-try mechanism indicating when thepredetermined plurality of attempts have been made.

11. The improvement of claim 10 further comprising:

a keyway through the face of the lock connecting with said limited-trymechanism; and

a key insertable in said keyway and coacting with said limited-trymechanism to reset said ratchet wheel permitting the lock to be openedby the use of the proper combination.

[2. The improvement of claim 8 wherein:

said holding pawl is releasable from said ratchet wheel by contact withthe fence-lever when the proper combination is used and said fence-leverenters the tumbler gates.

' 0 -0 h "UNITED STATES PATENT OFFICE 0 v CERTIFICATE 0F CORRECTION I Ptent-No. 3.786Q658'I Dated J 1974 ln ventefls) 0 Frank H. Swa'im I It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

1.. In elaim' jlihe 9, insert the wozlid' -b eingafter the word"mechanism". 2 cI L a-im l, line 10, correct theeword "mahiIpxilation"tbqi'ead -R1arIiipu1Ie1 or h 3. I In cl aifiS '16, I c o rr eci z the wozpd "ebafii'ng'? to read --coa'cti'ng--.

I I s gneq'j'an sealed rhi's- 19th d y of November 1974.

(SEAL) Attest I I Meet)? M. fcl soN JR. I ,c. MARSHALL DANN AttestingOfficer I Commissioner of Patents

1. An improvement in combination locks having tumblers with gates and afence-lever for improving the security thereof from unauthorizedmanipulation comprising a limited-try mechanism cooperating with saidtumblers and said fence-lever which prevents opening of the lock after apredetermined plurality of attempts have been made using the impropercombination, the action of said mechanism undetectable by amanipulation.
 2. The improvement of claim 1 wherein said limited-trymechanism includes blocking means preventing said fence-lever fromcooperating with said tumbler gates to preclude the opening of the lock.3. The improvement of claim 2 wherein said limited-try mechanism furtherincludes means for mechanically registering cumulatively the number ofunsuccessful attempts to open the lock.
 4. The improvement of claim 3wherein said limited-try mechanism further includes reset means topermit opening the lock when the proper combination is used before thepredetermined plurality of attempts have been made.
 5. The improvementof claim 4 wherein said limited-try mechanism further includes meanspermitting resetting by a tool from the outside of the lock after thepredetermined plurality of attempts have been made to open the lock. 6.The improvement of claim 5 wherein said limited-try mechanism furtherincludes means for monitoring the plurality of attempts to open thecombination lock on the face of the lock without notifying anunauthorized manipulator that the predetermined number has been reached.7. The improvement of claim 2 wherein the limited-try mechanism furtherincludes means for actuating an alarm when the predetermined pluralityof attempts have been made to open the lock.
 8. An improvement in acombination lock having tumblers with gates, a cam wheel, a fence-lever,and a dial on the face comprising: a limited-try mechanism comprising: apusher pawl cooperating with the fence-lever when it does not enter thegates; a ratchet wheel rotatably advanced one step by said pusher pawleach time the fence-lever comes in contact with said pusher pawl; aholding pawl coating with said ratchet wheel to hold it in the advancedposition; a cam surface having a slot on the side of said ratchet wheel;a lockout bar in slidable relationship with said cam and coacting withand precluding the entry of the fence lever into the tumbler gates whensaid lockout bar enters said slot in said cam surface, whereby saidlimited-try mechanism renders the lock unopenable after thepredetermined plurality of trys using the improper combination has beenmade and whereby said limited-try mechanism is reset by using the propercombination before the predetermined plurality of trys has been made. 9.The improvement of claim 8 wherein said limited-try mechanism furthercomprises: a tell-tale dial outside the lock and coupled with saidratchet wheel to indicate the plurality of attempts made to open thelock.
 10. The improvement of claim 9 further comprising: an alarmcoupled with said limited-try mechanism indicating when thepredetermined plurality of attempts have been made.
 11. The improvementof claim 10 further comprising: a keyway through the face of the lockconnecting with said limited-try mechanism; and a key insertable in saidkeywaY and coacting with said limited-try mechanism to reset saidratchet wheel permitting the lock to be opened by the use of the propercombination.
 12. The improvement of claim 8 wherein: said holding pawlis releasable from said ratchet wheel by contact with the fence-leverwhen the proper combination is used and said fence-lever enters thetumbler gates.